This article explains how to recover deleted IMAP messages from Outlook, and how to create a ribbon menu item for deleting emails. Instructions apply to Outlook 2019, 2016, 2013, 2010, 2007, and 2003.

When you delete a message in an IMAP account accessed through Outlook, it is not immediately deleted and Outlook does not move it to the Deleted Items folder. Instead, these messages are marked for deletion and sometimes hidden on purpose because you don't really need to see them. So you have to clean up the half-deleted emails to remove them from the server.

Here's how to set Outlook to permanently delete messages marked for deletion in IMAP email accounts:

In the Clean Up group, select Clean Up.